BUFFALO, N.Y. – Research on the communication trait of
verbal aggressiveness, which includes behavior like name calling,
ridicule, insults, racial epithets and threats, has tended to focus
on its social causes.

However, a new study by a team of researchers led by Allison Z.
Shaw, PhD, assistant professor of communication at the University
at Buffalo, has found that verbal aggression may have biological
causes that can be identified by the ratio of length of a
person’s ring finger (second digit) to the length of the
index finger (fourth digit).

It is the first study to use the 2D:4D ratio – considered
a measure of prenatal testosterone exposure – as a
determinant of verbal aggression.

The study, “The Effect of Prenatal Sex Hormones on the
Development of Verbal Aggression,” was published in the
Journal of Communication (Vol. 62 No. 5) and its authors include
Michael R. Kotowski, assistant professor of communication,
University of Tennessee, and Franklin J. Boster and Timothy R.
Levine, both professors of communication at Michigan State
University.

Shaw says prior research has suggested that the 2D:4D ratio can
be used as a measure of exposure to androgens in utero
(testosterone being a type of androgen) and a number of studies
have shown a correlation between the 2D:4D ratio and various
physical and behavioral traits.

The research team hypothesized that if prenatal exposure to
testosterone influences the 2D:4D ratio and high levels of prenatal
testosterone exposure are linked to verbal aggression, then digital
ratio could predict the trait of verbal aggression.

To test this, they first measured the finger length of adult
subjects from the point where fingers meet the palm to the tip,
then photocopied each hand, palm down and made the same
measurements. From these results they calculated each
subject’s 2D:4D ratio.

The subjects then filled out the Verbal Aggression Scale and the
HEXACO Personality Inventory and the Argumentativeness Scale.

The team found that men and women with smaller 2D:4D ratio
reported themselves to be more verbally aggressive.

Shaw points out that, when expressed in limited contexts, verbal
aggression can be beneficial to an individual but when expressed
injudiciously, may have negative influences by provoking job loss,
for example, or making it difficult to maintain close personal
relationships.

“These findings have implications for our understanding of
the proximal and distal causes of verbal aggression,” Shaw
says.

“They suggest,” she says, “that verbally
aggressive behavior may be provoked by biologically based
differences in people’s attention to potentially threatening
stimuli (such as a sigh), their appraisal of the stimuli as
threatening and the resulting decision to respond and produce
messages that are verbally aggressive.

“This study is the first step in gaining a better
understanding of this process,” says Shaw, “and may
allow us to develop more sophisticated techniques to inhibit such
types of responses.”

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